A Model-Independent Discussion of Quark Number Density and Quark Condensate at Zero Temperature and Finite Quark Chemical Potential

Generally speaking, the quark propagator is dependent on the quark chemical potential in the dense quantum chromodynamics （QCD）. By means of the generating functional method, we prove that the quark propagator actually depends on p4 ＋ iμ from the first principle of QCD. The relation between quark number density and quark condensate is discussed by analyzing their singularities. It is concluded that the quark number density has some singularities at certain # when T = 0, and the variations of the quark number density as well as the quark condensate are located at the same point. In other words, at a certain # the quark number density turns to nonzero, while the quark condensate begins to decrease from its vacuum value.

Effect of the interfacial electric field on the HER on Pt(111)modified with iron adatoms in alkaline media

The study of the hydrogen evolution reaction(HER)aimed to reach a deeper understanding of the parameters that control the rate of this reaction is of great importance given the technical relevance of hydrogen production as an energy vector in the so-called hydrogen economy.In previous works,laser-induced temperature jump(LITJ)experiments on Pt(111)modified with Ni(OH)_(2)in alkaline media have revealed the importance of the interfacial electric field in the rate of the HER.It was hypothesised that small amounts of Ni(OH)_(2)cause a decrease of the electric field because of a negative shift of the pzfc toward the onset of the hydrogen evolution.In this work,to test the validity of this hypothesis,the study has been extended to Pt(111)surfaces modified with Fe(OH)_(2).The modified surfaces have been studied voltammetrically,and the voltammetric charges have been analysed.The voltammograms show a peak in the hydrogen evolution region that suggest the transformation in the adlayer from Fe(II)to Fe(0).In agreement with the coulometric analysis,the voltammetric features in the OH adsorption region would be related with the oxidation to the+3 valence state.The results obtained with LITJ method reflect the existence of a strong interaction of the Fe oxophilic species with the water molecules,shifting the potential of maximum entropy away from the onset of the HER.Hence,the most catalytic surface is the one with the lowest Fe coverage.

Surface terminals reconstruction:The way to widen the output voltage of MXene-based aqueous symmetrical microsupercapacitors

The low anodic oxidation potential severely suppresses the output voltage(≤0.6 V)of MXene-based symmetrical aqueous microsupercapacitors(MSA-MSCs)employing acidic electrolytes.Herein,a surface terminals reconstruction mechanism on cathode of MSA-MSCs adopting aqueous neutral electrolyte(1 M Na_(2)SO_(4))is first revealed by systematical electrochemical experiments and in/ex-situ spectral analysis,which indicates that:the-O terminals on Ti3C2Tx flakes of cathode can combine with intercalated Na+cations during charging process to reconstruct into-ONa units to(i)inhibit the splitting reaction of adjacent water molecules,decreasing cathodic hydrogen evolution potential,more significantly,(ii)lower the potential of zero voltage(P0V)between the symmetrical electrodes to avoid anode oxidation,enabling full use of the unexploited potential range of cathode.Thus,the output voltage of the MSA-MSCs tremendously expanded from 0.6 V in acidic polyacrylamide(PAM)/1 M H_(2)SO_(4)hydrogel electrolyte to 1.5 V in neutral polyacrylamide/1 M Na2SO4 hydrogel electrolyte,boosting the corresponding areal energy density from 9.9 to 34.6μW·h·cm^(-2).The demonstrated deep insight on the surface terminals reconstruction mechanism for synchronously modulating the P0V between symmetrical electrodes and hydrogen evolution potential on cathode provides critical guidance for widening the cell voltage of MSA-MSCs with safer and more inexpensive neutral electrolytes.